Self-Controlled ARdrone (Part I) - Adding extra hardware.

On the previous entry, I showed my new Library ARdrone++. Now I want to show you in a few entries how to auto-control your ARdrone from a computer attached to it.

The computer
In my case, I use an Odroid U3, a small ARM-based computer with good relation weight-ComputerCapability.

Odroid U3 has a Cortex-A9 Quad Core 1.7Ghz CPU 2GB of RAM and a Mali-400 GPU. It weight ~28g without heatsink and 48g with it. Let me insist again on weight, this is very important because ARdrone is not designed to lift anything but itself.

Adding a new computer  carry a new trouble, it's power supply. There are two options here depending on the consumption of the computer. The first one is to use the USB of the ARdrone to steal to it energy. And the second one is add another battery to the drone. Let me show you pros and cons of both solutions:

• Use the on-board USB: This solution has one key advantage: No extra battery-No additional weight. The main disadvantage is that consumes ARdrone battery and has current limitations. So if you plan to use many USB peripherals you should pass to next solution. 

• Add a new battery: In this case I decided to use a one-cell Li-ion battery. this kind of batteries have high energy density. The only fact yo consider is that usually provide 3.7 output voltage, and the most of computers need 5V a power supply. To solve this trouble I take a Boost SMPS from a portable mobile charger (These has 2 pros, increase the voltage and can be use to recharge the battery):

Finally, to allow odroid.u3 to connect to ARDrone, we need a USB wifi module:

Assembly

Now we've everything!. The battery I chose was flat enough to be placed on the drone battery, if you have someone similar place there.

The best place for the computer is on the bottom due to space. The only issue is not to cover the ground sensors (Camera and US-sensor). Use some kind of double stick tape to attach it and for security, grab it with a pair of rubber bands (These will push it to the tape and prevent it to loose if tape lose stickiness due to vibrations).

And that's it! In future tutorials, I will show you how to connect the computer to the ARdrone and control it from inside!